Hello, Anybody have some in depth info on the path this signal takes. My issue is , turn on the radio mast goes up few seconds later down it goes. I have monitored the signal to the antenna and confirm the loss of the 12vdc drive up with or without the antenna unit plugged in.. The wiring diagram that i am using is from a 1998 XK8 and although i have a 2004 XKR believe to be accurate. it only shows a single wire going directly into radio head. Thinking simply that it would go to the on/off switch is a wish, more likely the switch signals some kind of driver circuit. Every once in awhile it will stay up always on first try after car sets overnight. Anyone ! !

 

The power antenna has two 12V inputs and a ground (return). I'm not sure how the connector on the unit is wired (which pins in the connector carry which voltage). One 12V comes from the ignition source (battery voltage through the ignition/key switch). The second comes from the 12V through the radio "head" unit. When both 12V signals are received at the antenna the motor is enabled and raises. As long as both 12V signals are received at the antenna the mast will remain up. When either 12V signal is removed the motor is enabled again and the mast lowers. There's a circuit board inside the antenna unit that controls the state of the mast based on the two 12V inputs. If yours goes up and then right back down it's definitely getting both 12V signals when you turn the radio on. It may be that one is being removed shortly after the radio is turned on or it may be that the circuit board inside the antenna is defective. I don't know how the 12V signal is routed through the radio. It may be as simple as a 12V output signal from the radio on/off switch or it may be buffered through a transistor or op-amp and then out to the antenna. The signal from the ignition I believe is only a connection from the ignition switch which has no electronics associated with it. I'm pretty sure it goes to more destinations in the car than just the antenna so if were dropping out you'd notice more problems than just the antenna mast. So the problem is likely in the circuit card in the antenna or the radio "head" unit. If you can find the pin-out of the antenna connector in the wiring harness you should be able to use a DVM to determine if the problem is in the 12V from the radio or not.

Good luck

 

Steven:
Sounds like you may have an intermittent GB (green-black) signal to the motor unit.
I am attaching my 2002 Handbook schematic:

Lead GB provides a +12v signal (IC20-18) to the motor unit only when the head unit is on. Lead NG (brown-green) provides an always on +12v signal (Boxed in 57) to the motor unit.
The switching logic takes place within the motor unit itself. When the GB +12v signal is present, this switching device mutes the NG +12v signal within the motor unit and activates the motor to raise the antenna until its upper limit is reached and disables the motor. This device stays activated until the GB signal is lost (until head unit turned off). Then the switching device switches back to seeing the +12v NG signal which activates the motor to lower the antenna until its lower limit is reached.
FYI: This GB lead is the same lead that some members including myself have installed an inline antenna disable switch.

 

Hello, thank you for the replies. I am losing signal ( 12vdc ) at the IC20-18 output and have the same schematic you show. Any knowledge or more importantly the detail of what takes place in the radio head to create that signal ! ! I was hoping for someone who actually repaired radio's would respond. Thanks Steve

 

Fellow members:
Allow me to apolgize for for my post#3. Although I only had good intent, my explanation, while having some truth, proved to have some operation errors which are beyond my knowledge of this systems logic. Whether that logic be in the in the head unit or the motor unit , I do not know (I suspect sampling and/or timing signals to also be present). If I could undo that post I would.

Steven:
Since you have traced the problem back to the head unit connector, the problem seems to be in the head unit. At this point, I do not know how daring that I would be to go into that unit.
Again, best of luck.